Fix clippy warnings and simplify check-rust workflow

[basfroman]

• fix all clippy warnings in keyfile.rs, utils.rs, wallet.rs, python_bindings.rs (redundant closures, manual strip, needless borrows, too_many_arguments, etc)
• remove redundant jobs from check-rust workflow (cargo-check-lints, cargo-fix, cargo-check-no-python, check-feature-propagation)
• switch all CI runners from SubtensorCI to ubuntu-latest
• add cargo-package-check job to check-rust workflow
• update yanked dependencies (futures-util, keccak)
• fix .gitignore pattern for nested .DS_Store files
• add Makefile for running checks locally